calendar/agents/skills/vercel-react-best-practices/rules/server-parallel-fetching.md

title, impact, impactDescription, tags

title	impact	impactDescription	tags
Parallel Data Fetching with Component Composition	CRITICAL	eliminates server-side waterfalls	server, rsc, parallel-fetching, composition

Parallel Data Fetching with Component Composition

React Server Components execute sequentially within a tree. Restructure with composition to parallelize data fetching.

Incorrect (Sidebar waits for Page's fetch to complete):

export default async function Page() {
  const header = await fetchHeader()
  return (
    <div>
      <div>{header}</div>
      <Sidebar />
    </div>
  )
}

async function Sidebar() {
  const items = await fetchSidebarItems()
  return <nav>{items.map(renderItem)}</nav>
}

Correct (both fetch simultaneously):

async function Header() {
  const data = await fetchHeader()
  return <div>{data}</div>
}

async function Sidebar() {
  const items = await fetchSidebarItems()
  return <nav>{items.map(renderItem)}</nav>
}

export default function Page() {
  return (
    <div>
      <Header />
      <Sidebar />
    </div>
  )
}

Alternative with children prop:

async function Layout({ children }: { children: ReactNode }) {
  const header = await fetchHeader()
  return (
    <div>
      <div>{header}</div>
      {children}
    </div>
  )
}

async function Sidebar() {
  const items = await fetchSidebarItems()
  return <nav>{items.map(renderItem)}</nav>
}

export default function Page() {
  return (
    <Layout>
      <Sidebar />
    </Layout>
  )
}